// Copyright © 2020 The Things Network Foundation, The Things Industries B.V.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package udp

import (
	"sync"
	"time"
)

type timestamps struct {
	position int
	mu       sync.RWMutex
	items    []time.Time
}

func newTimestamps(count int) *timestamps {
	return &timestamps{
		items: make([]time.Time, count),
	}
}

// Append adds new timestamp and returns oldest.
func (i *timestamps) Append(val time.Time) time.Time {
	i.mu.Lock()
	defer i.mu.Unlock()
	result := i.items[i.position]
	i.items[i.position] = val
	i.position = (i.position + 1) % len(i.items)

	return result
}
